Just over half a century ago, Harvard Law School provided the setting for a debate between the two most influential British and American legal theorists. H.L.A. Hart, Professor of Jurisprudence at Oxford, was invited to give the Law School's annual Holmes Lecture. Hart took this opportunity to enunciate the kernel of his emerging theory of legal positivism, staking out his claim to be the 20th Century successor to Jeremy Bentham and John Austin. Lon L. Fuller, Carter Professor of General Jurisprudence at Harvard, and a man who had long ploughed a rather lonely jurisprudential furrow as a scholar and teacher committed to exploring the morality of law, demanded a right to reply. The rest, as they say, is history. In this paper, I revisit that history, and give it a somewhat different interpretation from the one which it has generally received. My argument is that Fuller was at an inevitable disadvantage in the debate. Because of Hart's agenda-setting position, the terms of the debate are those of analytic legal philosophy: and the reception of the debate has, understandably, both interpreted and evaluated Fuller's argument largely in terms of criteria internal to that discipline. But while Hart's Holmes lecture can justly be seen as exemplary of his broader contribution, Fuller's most original interventions in legal scholarship originated not so much in a philosophical view but rather in a broader socio-legal and interdisciplinary interpretation of legal institutions and processes. Though Fuller might have drawn on this broader work to raise questions about Hart's approach, he did not do so as effectively as he might have done. Hence the salience to Fuller's reputation of his role as Hart's natural law opponent marginalises some important strengths of his scholarship. I preface this argument with a historical and biographical sketch: introducing the protagonists and their intellectual and personal preoccupations; setting the scene for the debate in terms of contemporary legal scholarship and legal education; and providing a richer context in which to assess the debate's overall significance for legal scholarship today.